I've ordered a portable surge protector from Camping World and expect to have it by next Thurs. Amazingly, I've managed to be OK without using one during my entire full time RVing career. I now feel that for the cost of one of these units (about $100+) the peace of mind is worth it.

If you're using one let us know if it has ever "saved your bacon" on occasion.

I use whole house wired one.
A while ago I plugged into the 30 amp outlet and the surge protector(Electrical Management System) told me the circuit was not grounded. I informed the campground host and showed him the indicator on the equipment. He said people had been using that spot for weeks and that means there is nothing wrong with the outlet. I said, no it doesn't. It simply means the users were lucky and no one was electrocuted. I moved to a different spot then quietly posted a note on the other box alerting the next user to be sure to test the ground before hooking up.

On several occasions it's alerted me to a low voltage condition that can be harmful to electric motors like the A/C.

I have been using a Progressive 'surge' surpresser for a number of years now. It has the ability to monitor the power coming into my coach. It has, on several occasions, alerted me to the fact that the power coming in to my coach was low voltage-as low as 103 volts- which as ed6713 indicated, could be harmful to A/C's and other electric motors. This problem is not limited to certain, off brand campgrounds. I found this problem in very large, prominent campgrounds like Disney's Fort Wilderness, Hershey High Meadow, and most recently, Sugarloaf Key KOA in Key West. It got to the point where the surge protector would shut down the power to my coach and reset a short time later. I feel that with all the electronics in today's coaches, it is well worth the investment of a few hundred dollars to protect the coach.
JMHO.